legal: strengthen disclaimer, liability, and warranty language

- LICENSE: expanded warranty disclaimer covering silent failures from
  third-party changes, coverage gaps, regulatory non-compliance, and
  commercial licensee expectations. Explicit limitation of liability
  for privacy breaches, identity theft, and regulatory penalties.
- PRIVACY.md: added limitations section covering third-party changes,
  coverage gaps, user responsibility, and compliance disclaimer.
- README.md: detailed disclaimer with specific scenarios — site API
  changes, coverage gaps, user verification responsibility, and
  commercial license scope.
- Popup: expanded footer warning about third-party changes and user
  responsibility.
- Options page: added footer disclaimer with LICENSE link, updated
  version to 0.9.0.

https://claude.ai/code/session_01KF4i7Ra7zCEDskxDBaNtcT

src/options/options.html

@@ -629,7 +629,10 @@
     </section>
 
     <footer>
-      <p>Silent Send v2.0.5</p>
+      <p>Silent Send v0.9.0</p>
+      <p style="font-size:11px;color:#9ca3af;margin-top:6px;max-width:600px">
+        Silent Send is a convenience tool, not a security guarantee. Third-party sites may change how they send data at any time, which can cause missed substitutions without warning. You are responsible for verifying your data before sending. See the <a href="https://github.com/outis1one/silent-send/blob/main/LICENSE" target="_blank" style="color:#6b7280">LICENSE</a> for full terms.
+      </p>
     </footer>
   </div>